Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932069AbaKKLMo (ORCPT ); Tue, 11 Nov 2014 06:12:44 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:57962 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752572AbaKKLLn (ORCPT ); Tue, 11 Nov 2014 06:11:43 -0500 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: "Eric W. Biederman" , Andy Lutomirski , Luis Henriques Subject: [PATCH 3.16.y-ckt 169/170] mnt: Prevent pivot_root from creating a loop in the mount tree Date: Tue, 11 Nov 2014 11:08:48 +0000 Message-Id: <1415704129-12709-170-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1415704129-12709-1-git-send-email-luis.henriques@canonical.com> References: <1415704129-12709-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.7-ckt1 -stable review patch. If anyone has any objections, please let me know. ------------------ From: "Eric W. Biederman" commit 0d0826019e529f21c84687521d03f60cd241ca7d upstream. Andy Lutomirski recently demonstrated that when chroot is used to set the root path below the path for the new ``root'' passed to pivot_root the pivot_root system call succeeds and leaks mounts. In examining the code I see that starting with a new root that is below the current root in the mount tree will result in a loop in the mount tree after the mounts are detached and then reattached to one another. Resulting in all kinds of ugliness including a leak of that mounts involved in the leak of the mount loop. Prevent this problem by ensuring that the new mount is reachable from the current root of the mount tree. [Added stable cc. Fixes CVE-2014-7970. --Andy] Reported-by: Andy Lutomirski Reviewed-by: Andy Lutomirski Link: http://lkml.kernel.org/r/87bnpmihks.fsf@x220.int.ebiederm.org Signed-off-by: "Eric W. Biederman" Signed-off-by: Andy Lutomirski Signed-off-by: Luis Henriques --- fs/namespace.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/namespace.c b/fs/namespace.c index e544a0680a7c..f24161a45b06 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2840,6 +2840,9 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, /* make sure we can reach put_old from new_root */ if (!is_path_reachable(old_mnt, old.dentry, &new)) goto out4; + /* make certain new is below the root */ + if (!is_path_reachable(new_mnt, new.dentry, &root)) + goto out4; root_mp->m_count++; /* pin it so it won't go away */ lock_mount_hash(); detach_mnt(new_mnt, &parent_path); -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/